In the developing nervous system, initially promiscuous synaptic connections are remodeled by activity-dependent mechanisms, with axons strengthening their connections with some targets while completely disconnecting from others. In the neocortex, this process has been most thoroughly studied in the developing primary visual cortex, where decorrelating the activity of the two eyes dramatically reduces cortical binocularity. These functional changes in cortical physiology are widely accepted to be anchored in long-lasting changes in the efficacy of synaptic connections. However, the specific mechanisms by which synaptic plasticities lead to changes in the function of cortical circuitry remain elusive. The major objective of the work proposed here is to determine where in the cortical circuit experience-dependent changes in binocular responses are first observed, track the progression over time, and test the hypothesis that these changes are anchored in anatomical changes in synaptic connectivity. To address these questions, techniques such as 2-photon laser scanning microscopy, intrinsic signal optical imaging, and single-unit recordings, will be used to map circuit plasticity and follow changes in synaptic connectivity in vivo.